Most modern aircraft include an auxiliary power unit ("APU") as standard operational equipment. Typically, the APU is positioned in a compartment located in the tailcone portion of an aircraft. Federal Aviation Administration regulations require a means for overboard draining of all flammable liquids that might be leaked by the APU or otherwise may accumulate in the APU compartment. Heretofore, the draining method most commonly employed included one or more drainage tubes connecting the compartment to an overboard drain port. Gravity flow was relied upon to force the liquids through the drainage tubes and drain port.
Unfortunately, a negative pressure differential often exists within the compartment, that is, pressure within the compartment is often lower than the pressure at the aircraft drain port. In such instances, reliance upon gravity flow is generally insufficient inasmuch as the liquid pressure head needed to overcome the negative pressure differential may entail a dangerously large upstream liquid accumulation. Accordingly, what is needed is an APU compartment drainage system that ensures thorough compartment draining under maximum negative pressure differential conditions for any given aircraft.